资源环境科技发展态势分析平台

The East Asia/Pacific (EAP) teleconnection can substantially modulate weather anomalies over eastern Asia during summer. Wavelet analyses, including ensemble mean power spectrum and accumulated frequency of significant components, highlight 10-30-day oscillations in the EAP index. The influences of these low-frequency oscillations on weather anomalies are further investigated via both phase-dependent and lead-lag composites. On 10-30-day scales, a tripole structure of precipitation anomalies and a temperature seesaw form concurrently over adjacent regions along eastern Asia. These anomalies last for about 1week, constituting anomalous weather spells with possible extreme values around the peak/valley phases. For cold spells over Northeast Asia during positive phases, the low-frequency easterly is the determinant factor. On one hand, it advects cold air from the sea east of the land. On the other hand, it conveys moisture to form low-based clouds, which are effective in inhibiting incoming solar radiation. While, for cold spells over central-eastern Siberia during negative phases, regional-scale precipitation and cold advections conveyed by anomalous northerlies combine to make contributions. Both hot spells over central-eastern Siberia/Northeast Asia during positive/negative phases mainly result from the adiabatic heating and increasing solar radiation, both of which are attributed to strong descent in response to upper-level convergences. In addition to great intensity, the high-impact property of these simultaneous weather anomalies also arises from their long duration and large spatial extent. By taking advantages of the quasi-periodicity of the 10-30-day oscillations, better predictions of these simultaneous weather anomalies/extremes would be anticipated.